In mathematics, omega function refers to a function using the Greek letter omega, written ω or Ω.

(big omega) may refer to:

• The lower bound in Big O notation, , meaning that the function dominates in some limit
• The prime omega function , giving the total number of prime factors of , counting them with their multiplicity.
• The Lambert W function , the inverse of , also denoted .
• Absolute Infinity

(omega) may refer to:

• The Wright Omega Function , related to the Lambert W Function
• The Pearson–Cunningham function
• The prime omega function , giving the number of distinct prime factors of .